A gas turbine engine typically includes a fan section, a compressor section, a combustor section and a turbine section. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-energy exhaust gas flow. The high-energy exhaust gas flow expands through the turbine section to drive the compressor and the fan section. The compressor section typically includes low and high pressure compressors, and the turbine section includes low and high pressure turbines.
The turbine section drives a fan that provides a substantial portion of thrust generated by the engine. Guide vanes aft of the fan direct airflow into the compressor section to increase compressor efficiency. Airflow into the fan maybe directed to some extent by a nacelle structure surrounding the fan blades, but otherwise is not pre-conditioned.